|
Search: id:A020994
|
|
|
| A020994 |
|
Primes that are both left-truncatable and right-truncatable. |
|
+0
11
|
|
| 2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Two-sided primes: deleting any number of digits at left or at right, but not both, leaves a prime.
Primes in which every digit string containing the most significant digit or the least significant digit is prime. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 24 2003
|
|
REFERENCES
|
Angell, I. O. and Godwin, H. J. "On Truncatable Primes." Math. Comput. 31, 265-267, 1977.
David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 178 (Rev. ed. 1997).
|
|
LINKS
|
P. De Geest, The list of 4260 left-truncatable primes
Index entries for sequences related to truncatable primes
|
|
MATHEMATICA
|
tspQ[n_] := Module[{idn=IntegerDigits[n], l}, l=Length[idn]; Union[PrimeQ/@(FromDigits/@ Join[Table[Take[idn, i], {i, l}], Table[Take[idn, -i], {i, l}]])]=={True}] Select[Prime[Range[PrimePi[740000]]], tspQ]
|
|
CROSSREFS
|
Cf. A033664, A024785, A032437, A024770, A052023, A052024, A052025, A050986, A050987.
Sequence in context: A104179 A096148 A124674 this_sequence A085823 A100552 A155873
Adjacent sequences: A020991 A020992 A020993 this_sequence A020995 A020996 A020997
|
|
KEYWORD
|
nonn,fini,full,base
|
|
AUTHOR
|
Mario Velucchi (mathchess(AT)velucchi.it)
|
|
EXTENSIONS
|
Corrected by David W. Wilson.
Additional comments from Harvey P. Dale (hpd1(AT)nyu.edu), Jul 10 2002
|
|
|
Search completed in 0.002 seconds
|
